HCO3, the Bicarbonate ion, is the main alkaline factor in almost all water.

Alkalinity serves as a buffer, neutralizing acids. It is of no great significance in most situations, but it is a problem in areas like the beverage industry, boiler towers, cooling towers, and the textile industry. Excessive alkalinty, for example, can interfere with dying of textiles and it defeats the acidity of fruit flavors in beverages.

Alkalinity is a measure of the capacity of water or any solution to neutralize or “buffer” acids. This measure of acid neutralizing capacity is important in figuring out how “buffered” the water is against sudden changes in pH.

Alkalinity should not be confused with pH. pH is a measure of the hydrogen ion (H + ) concentration, and the pH scale shows the intensity of the acidic or basic character of a solution at a given temperature. The reason alkalinity is sometimes confused with pH is because the term alkaline is used to describe pH conditions greater than 7 (basic).
The most important compounds in water that determine alkalinity include the carbonate (CO3 2- ) and bicarbonate HCO3 -) ions.

Carbonate ions are able to react with and neutralize 2 hydrogen ions (H + ) and the bicarbonate ions are able to neutralize H + or hydroxide ions (OH - ) present in water. The ability to resist changes in pH by neutralizing acids or bases is called buffering.

Treatment: Bicarbonate alkalinity can be reduced by aeration, which reduces free carbon dioxide. It can also be treated by feeding acid to lower pH. Strong Base Anion exchange also reduces alkalinity.

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